maybe this will simply turn out to be a gap in my understanding about multicast
addressing, but my EX4550/4200 VC is not pruning multicast how I would expect.
I have vlan defined with an RVI. I have enabled igmp for that vlan interface.
I have two hosts that are members of the same vlan (server A and server B, vlan
123). igmp-snooping is on for all vlans (factory default setting).
I am using iperf to send/receive test multicast streams from server A to server
B.
With igmp-snooping and igmp running on the vlan, If I send a stream via iperf
from server A, I do not expect that stream to show up on server B until I start
the iperf server at the same multicast address. I expect the switch to not
flood the traffic to all ports in the vlan (including serverB ) but instead
wait until a server explicitly joins the group.
This does not appear to always be true. I obviously haven't tested every
multicast address, but it seems that pretty much all multicast traffic directed
to 224.0.0.0-239.0.0.255 will cause the switch to flood traffic to all ports in
the vlan.
But addresses from 239.0.1.0 and up seem to work as I expect. If server A
sends to 239.0.1.1 and I listen for traffic to that address on server B, I
don't see anything. It seems the switch is pruning as I would expect. As soon
as I start the multicast iperf listener on server B for 239.0.1.1 then my
tcpdump immediately lights up with the multicast traffic- again as I would
expect. In fact the opposite behavior seems to occur- with the 239.0.1.1
address, if I don't have igmp configured on the vlan at all (delete protocols
igmp interface vlan.123) the switch does NOT flood multicast traffic for that
address. I see nothing arrive on server B. this is also unexpected.
can anyone set me straight?
also- what I'm trying to do is relatively simple but maybe I'm going about it
the wrong way. I have groups of servers in the vlan that use multicast packets
as a periodic "heartbeat" to keep track of each other. I'd like to make sure
the multicast heartbeat only goes to other servers that subscribe to the same
multicast address- not send it to every server in the vlan. does my config
seem like a valid way to do this? I don't need to route the multicast across
subnets.
thanks!
-andy
here are the relevant config snippets and the iperf and tcpdump commands I'm
using:
# show vlans 123
vlan-id 123;
l3-interface vlan.123;
# show interfaces vlan.123
family inet {
address x.x.x.x/24;
}
# show protocols
igmp {
interface vlan.123;
}
igmp-snooping {
vlan all;
}
iperf client (sender): iperf -c 239.0.1.1 -u --ttl 2 -t 30 -i 5
iperf server (receiver): iperf -s -u -B 239.10.1.1 -i 5
tcpdump example: tcpdump -nn host 239.0.1.1
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